The present invention relates to a failsafe control system for an electromagnetically driven valve for opening and closing an intake port or exhaust port of an internal combustion engine.
It is known to construct intake and exhaust valves of an internal combustion engine from electromagnetically driven valves and control the valves in accordance with desired opening and closing characteristics for thereby obtaining desired intake and exhaust efficiencies as disclosed in Japanese Patent Provisional Publication No. 9-195736.
In this kind of electromagnetically driven valve, an energizing current supplied to an electromagnetic actuator is controlled so as to reduce the speed of the valve at the end of movement of the valve toward a fully open position or a completely closed position (i.e., at the time of seating of the valve or contact of an armature with an electromagnet) to nearly zero and thereby make smaller a noise resulting from the seating of the valve or contact of the armature with the electromagnet. For example, when the valve is held in a half or partly open position under the urge of valve springs due to a failure in movement of the valve toward the fully open position or the completely closed position, which is caused, for example, by an increased pressure within a cylinder or an increased friction against movement of the valve, there will be caused not only a misfire due to an insufficiently compressed mixture but a backfire due to simultaneous opening of the intake and exhaust valves, which provides communication between an intake system and an exhaust system and an influence to intake conditions (e.g., pressure and composition) of other cylinders.
It is accordingly an object of the present invention to a failsafe control system and method for an electromagnetically driven valve of an internal combustion engine which can solve the above noted problems inherent in the prior art systems.
It is a further object of the present invention to provide a failsafe control system and method for electromagnetically driven intake and exhaust valves of an internal combustion engine which can provide a proper failsafe control in case of malfunction of the valves.
To accomplish the above objects, there is provided according to an aspect of the present invention a failsafe control system for a valve electromagnetically driven by an actuator for opening and closing a combustion chamber of an internal combustion engine, the actuator having a pair of electromagnets, an armature interposed between the electromagnets and attached to the valve, and a pair of springs disposed on the opposite sides of the armature for urging the valve toward a neutral position, the failsafe control system comprising a control unit which includes a determining section that determines whether the valve can be moved into an open position at the time the valve is driven to open, and a failsafe section that drives the valve to a close position when the determining section determines that the valve cannot be moved into the open position.
According to another aspect of the present invention, there is provided a f safe control method for a valve electromagnetically driven by an actuator for opening and closing a combustion chamber of an internal combustion engine, the actuator having a pair of electromagnets, an armature interposed between the electromagnets and attached to the valve, and a pair of springs disposed on the opposite sides of the armature for urging the valve toward a neutral position, the method comprising determining whether the valve can be moved into an open position at the time the valve is driven to open, and driving the valve to a close position when it is determined that the valve cannot be moved into the open position.